I think as has been said, lots of boys are actually close to the mums and dads... as well as girls. I think girls/daughters do tend to gravitate towards the mums and dads more than boys do when they're older. But some boys will still be close. IME, when a daughter gets married, the couple do tend to gravitate more towards HER parents, and her parents get to see the grandkids more. I know a lot more daughters who are close to their parents, than sons who are. As I say, some sons remain close, but more daughters do. (IME and IMO.)
The only worry I think there should be for people if they've got boys - is if they get married and have kids with a woman, and the relationship breaks up, there's a possibility that you might see a lot less of the grandchildren, and even have them stripped from your life.
I have known many cases like this over the decades... where the paternal grandparents have been shut out when the couple splits, and the grandchildrens mother takes them from the paternal parents lives.
I know four cases right now, of couples who have broken up in the last 3 years. The grandparents, are all the 'paternal' grandparents (their SON is the father.) They are all absolutely devastated, as the mothers of their grandchildren, (their daughter-in-laws) have gone off with other men, or just left the county and moved 100s of miles away with the children. A couple of them haven't seen their grandchildren for over a year now. And they are absolutely devastated.
When it's a couple with an adult daughter, and she splits up with her husband, this doesn't tend to happen. The maternal grandparents definitely trump the paternal grandparents in a break up ... and to be honest with you, they'll generally trump the paternal grandparents before they're broken up. That doesn't mean the paternal grandparents will always be left out, or pushed out, but yes, for sure, the maternal ones definitely trump the paternal ones most of the time... People can deny this, but it's true.