Mr Sotong,
I reckon you are not very close with your father.
And your family situation is such that , you and your siblings
are old enough to take care of yourself.
Your father has paid off the house with not much debt.
He probably feels that he is no longer needed in the family, and
he is bored with the mundane routine of family life. Especially if
the bonds between father and children is not a close one.
So it is very tempting for a man his age to seek a second life
elsewhere.
You as the child can play a part to keep the family
together.
Going off on your own and ignoring the issue will only
contribute to the disintegration.
It is time.. you call him up and sit him down and have a man to
man talk.
Just because you are the child.. does not means you cannot be
actively involved in the family relationship.
