Donna: Well, if you guys are married then that means you two are brother and sister.
Kelly: ...Oh. My. God.
All 4 Love by Color Me Badd
Do You Believe in Magic by The Lovin' Spoonful
The episode concludes with Luke Perry and Shannen Doherty doing a public service announcement for the Red Cross.
Baby Makes Five
This is a 1983 television series.