Back in Sims 2 that was an actual plotpoint in my Strangetown at one time. I was playing Circe Beaker and her townie love (I don't remember that one's name), and they managed to get pregnant via mad science (aka mods), hoping for a genetics defying boy. They got two girls. Good times!
Nowadays I don't think this issue is worth being upset about, since we have ways to correct or prevent getting boys from a double xx couple: Giving the baby a female name and switching it to female soon as it leaves the crib (pretending it has always been a girl) or feeding the mother strawberries.