Because women are the main caregivers, it is easier to get to know her side of the family. When realtionships break up sometimes children become the tools by which adults hurt each other. e.g. you're not seeing the children or the man not only breaks up with the woman but also with his children.
It's the man's responsibility to introduce his children to his family. Lots of kids are walking around and don't know the identity of their paternal relatives. They could even be dating their paternal cousins or worse still their half siblings. Also most people see the terms aunt, uncle, grandmother as just a name when in fact it is a title that requires an action, it is a responsibility and a role.
A lot of kids will say that they don't like their paternal relatives and that is mainly because they don't know them and cannot identify with them. On the other hand, many of those relatives don't even know of the child's existance or didn't care to know. Years ago you could see a child on the streets and know that it was your relative. Now-adays you could be seen that same individual on a daily basis and not have a clue that you have some blood connection.