Here are several ideas:
1. How about a mom and her son are about to go bankruptcy? Mother is a widow finding ways to make a living. Son steps in to help his mother in household chores, earning money, develop skills and build a romantic relationship with the mother. There are two ways build relationship with the mother. It's either through love or lust. Lust does not necessarily mean corruption but mom will eventually fall into lewd thoughts to do lust with son. Love is more on romance and build trust.
2. Family goes on a vacation. Mother, dad, daughter and son are on a cruise but the cruise was attacked by a mysterious sea creature. Father dies because he saved his family from getting drowned. Son steps in to do heroic things to save his family. Eventually, he developed a romantic relationship with mom and sister.
3. Lone Mother remaster or remake.
4. Civil war happened within a country. Mother was kidnapped by insurgents. Son will develop his skills to save his mother from kidnappers. In his adventure, he will meet several strangers including some attractive women that will help to find his mother.
5. A very short game. Mom and son lives in a small village in Medieval Era. Son builds fire, hunts fish and fights wild animals to keep their home safe. Mom falls in love with son for being such a hero in her life. Characters must be few since this is a short game.