No; it's not supposed to make sense. Both Lahmard Tate and Vivica Fox are too young to play Shawn Wayans's (Ashtray's) parents. The filmmakers were exaggerating to make a joke. Supposedly, women in "the hood" have children very young.
It's a satire on how actors get cast as parents and their children, despite being a few years apart in age. In particular, it's a joke on the casting of Boyz n the Hood, the main movie it's parodying throughout, where Laurence Fishburne was paying Cuba Gooding Jr.'s Father despite being only seven years older than him in real life. Personally, it's my favorite bit of the whole movie, the jokes about how young Ashtray's Father is always cracks me up.
It's not supposed to make sense. It's a joke about people in the hood having kids very young, and plus the small age difference b/w Laurence Fisburne and Cuba Gooding Jr. in Boyz in the Hood.
Same with Angela Bassett, she played Cuba Gooding Jr's mother in "Boyz In the Hood" and she about 10 years older than Gooding. So the joke is pretty much all around.