Best way to resolve this, considering sons are currently far superior for clan growth and pregnancy chances get lower the more kids you have, is to make it so the more daughters or sons you have the more likely the other is to be born.
Currently if your first 2-3 kids are daughters you're potentially not having any sons the rest of the game, which just sucks for anyone playing a longer game. It's RNG that doesn't add much other than frustration to the game.
Alternatively, daughters could be handled differently. Maybe you can pay an extra fee to have their husbands join your clan instead of vice versa. And/or, any daughters you marry off don't count toward child count for purposes of pregnancy chance.
If you're going to feature a dynasty system you don't want it to be complete RNG whether people have heirs or not.
I'd add that I've seen this complained about in several posts on these forums and on reddit, so it's not an uncommon issue.