I don't think this is much of a challenge as it is a see-how-high-of-a-high-score-your-can-get. Any suggestions on how to make it harder are welcome.

You have to make two male (or female) Sims in college. Get them to fall in love with each other, but also find them a spouse of the opposite sex. Scoring starts after graduation. Keep your gay Sims (secretly) together for as long as possible. The challenge ends when one of them dies, then add half the daily relationship of the survivor to your score.

Scoring:
+10 for every child each one has.
+10 for each woohoo with each other a day, +1 for any extra.
+15 for any woohoo at home, when someone else is home.
+5 for each good date, +10 for each great date, and +15 for each dream date with each other.
+5 for each vacation together (counts as one day for woohoo)
-5 for each day they're not married to the opposite sex.
-50 for getting caught cheating (by spouse, children, or other relatives)
-50 for divorce
-10 for each 3rd party Sim to catch yours together, whether or not anyone is married.