QRectF TreeViewNode::boundingRect() const {
    return QRectF(-25, -25, 50, 50);
}

fixed it instantly.. such a silly mistake, it's almost as if I started learning about Qt last week.. (it's true).
What can I say, thank you so much to everyone for your time and your suggestions, I'll make sure to remove m_scene and use scene() as well and keep learning more in detail about the classes I'm using. Thank you!

@nance97 said in QWidget::mousePressEvent() not called:

QRectF TreeViewNode::boundingRect() const {
return QRectF();
}

This looks suspicious. Verify that your position and your boundingRect are where you expect them to be.

I would call it more than suspicious.

QGraphicsItem::boundingRect()

This pure virtual function defines the outer bounds of the item as a rectangle; all painting must be restricted to inside an item's bounding rect. QGraphicsView uses this to determine whether the item requires redrawing.

boundingRect() is also used for the default
QGraphicsItem::shape()

The shape is used for many things, including collision detection, hit tests, and for the QGraphicsScene::items() functions.
The default implementation calls boundingRect() to return a simple rectangular shape, but subclasses can reimplement this function to return a more accurate shape for non-rectangular items. For example, a round item may choose to return an elliptic shape for better collision detection.

QRectF TreeViewNode::boundingRect() const {
return QRectF();
}

void TreeViewNode::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) {
Q_UNUSED(option)
Q_UNUSED(widget)
painter->drawEllipse(-25, -25, 50, 50);
painter->drawText(QRectF(-25, -25, 50, 50), Qt::AlignCenter, QString::fromStdString(m_node->getPatient()->get_Name()));
}

This looks suspicious. Verify that your position and your boundingRect are where you expect them to be.
You could start by painting the boundingRect and compare it with your drawn item. If you paint outside the item's boundings, you wont receive events, when clicking inside this area.

There is a lot stuff going on, that is not needed or could/should be done "cleaner".
For example, a QGraphicsItem / -Object doesn't need to hold the scene as member, since you can access it any time with scene()
(https://doc.qt.io/qt-6/qgraphicsitem.html#scene)

At this point you might start a brand new standalone minimum compilable example to verify it works there? Then build up towards your code if so.

protected:
void mousePressEvent(QGraphicsSceneMouseEvent* event) override;

Maybe you can post the whole class

I'll do that since it's not too long and I really have no idea what is going on, thank you both for taking a look in the first place! Not shown is the mousePressEvent method declared protected in the header file and implemented as shown above, am I doing something blatantly wrong?

//TreeViewNode.h
class TreeViewNode : public QGraphicsObject {
    Q_OBJECT

private:
    node* m_node;
    Family_tree* m_family;
    QGraphicsScene* m_scene;
    static std::set<node*> addedNodes;

public:
    TreeViewNode(node* node, Family_tree* family, QGraphicsScene* scene);
    TreeViewNode* getTreeViewNode(node* n);
    node* getNode() const;
    static void clearAddedNodes();
    void updateNode(Patient& patient);
    QRectF boundingRect() const override;
    void drawBranches(QPainter* painter);
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
};

////TreeViewNode.cpp
std::set<node*> TreeViewNode::addedNodes;

TreeViewNode::TreeViewNode(node* node, Family_tree* family, QGraphicsScene* scene) : m_node(node), m_family(family), m_scene(scene) {
    setFlag(ItemIsFocusable);
    m_scene->addItem(this);
    addedNodes.insert(m_node);
    qDebug() << "Scene item count: " << m_scene->items().count();

    if (m_node->getFather()) {
        auto father = m_node->getFather();
        if (addedNodes.count(father) > 0) {return;}
        TreeViewNode* fatherNode = new TreeViewNode(m_node->getFather(), family, m_scene);
        fatherNode->setPos(-50, -100);
    }

    if (m_node->getMother()) {
        auto mother = m_node->getMother();
        if (addedNodes.count(mother) > 0) {return;}
        TreeViewNode* motherNode = new TreeViewNode(m_node->getMother(), family, m_scene);
        motherNode->setPos(50, -100);
    }

    if (m_node->getSpouse()) {
        auto spouse = m_node->getSpouse();
        if (addedNodes.count(spouse) > 0) {return;}
        TreeViewNode* spouseNode = new TreeViewNode(m_node->getSpouse(), family, m_scene);
        spouseNode->setPos(100, 0);
    }

    int childCount = 0;
    for (auto child : m_node->getChildren()) {
        if (addedNodes.count(child) > 0) {return;}
        TreeViewNode* childNode = new TreeViewNode(child, family, m_scene);
        childCount++;
        double xPos, yPos;
        xPos = pos().x() + 50 + 100 * (childCount - (m_node->getChildren().size() + 1) / 2.0);
        yPos = pos().y() + 100;
        childNode->setPos(xPos, yPos);
    }
}

TreeViewNode* TreeViewNode::getTreeViewNode(node* n) {
    for (auto item : m_scene->items()) {
        TreeViewNode* treeViewNode = dynamic_cast<TreeViewNode*>(item);
        if (treeViewNode && treeViewNode->getNode() == n) {
            return treeViewNode;
        }
    }
    return nullptr;
}

node* TreeViewNode::getNode() const {
    return m_node;
}

void TreeViewNode::clearAddedNodes() {
    addedNodes.clear();
}

void TreeViewNode::updateNode(Patient& patient) {
    m_node->setPatient(patient);
}

QRectF TreeViewNode::boundingRect() const {
    return QRectF();
}

void TreeViewNode::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) {
    Q_UNUSED(option)
    Q_UNUSED(widget)
    painter->drawEllipse(-25, -25, 50, 50);
    painter->drawText(QRectF(-25, -25, 50, 50), Qt::AlignCenter, QString::fromStdString(m_node->getPatient()->get_Name()));
}

Maybe you can post the whole class,

Or even better, a minimal example that demonstrates the problem.

I might have to consider a different solution

You dont have to, since it's the right way. Both ways (QGraphicsObject subclass or custom class derived from QGraphicsItem and QObject, which actually is the same as QGraphicsObject) should work.

Maybe you can post the whole class, since there must be something going on, so that you dont receive click events
Eventually a boundingRect issue, as mentioned by @jeremy_k or something else...

I'm working on a TreeViewNode class derived from QObject and QGraphicsItem,

Another option is to inherit from QGraphicsObject.

I made sure to include the setFlag(QGraphicsItem::ItemIsSelectable); method in the class constructor and I overloaded mousePressEvent like so:

void TreeViewNode::mousePressEvent(QGraphicsSceneMouseEvent *event) {
    if (event->button() == Qt::LeftButton) {
        qDebug() << "Mouse pressed on node: " << m_node->getPatient()->get_Name().c_str();

Making the item selectable isn't necessary to receive mouse events. In the following example, the left half of the item receives mouse presses because that falls within the area reported by QGraphicsItem::shape(). The right half of the text is displayed, but does not respond to clicks.

class Item : public QGraphicsTextItem {
    Q_OBJECT
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *event) {
        qDebug() << "mousePressEvent" << event->pos();
    }
public:
    Item(QGraphicsItem *parent = nullptr): QGraphicsTextItem(parent) {
        setPlainText("A|B");
        setFlag(QGraphicsItem::GraphicsItemFlag::ItemIsSelectable, false);
    }
    QPainterPath shape() const {
        QPainterPath path;
        QRectF rect = boundingRect();
        rect.setWidth(rect.width() / 2);
        path.addRect(rect);
        return path;
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QGraphicsScene scene;
    QGraphicsView view(&scene);
    Item item;
    scene.addItem(&item);
    view.show();
    return a.exec();
}