I started with the Silver family, branched off to the Verde family (since Gertrude's new husband comes from there), and then did the Gold family (because oldest son Warren married into it).  Since Lionel and Jason--the second and third sons--still live with Gertrude, I'll talk about fourth son Harrison, who moved out recently.

Harrison Silver had been in a relationship with his older brother Lionel.  However, when he found out that Lionel was not only cheating on him with a woman but actually intended to marry her and move her into the Silver household (Grant had already moved in with his mistress/new wife), the betrayal was too much.  He took a walk around town to cool off.

During his solitary trek he met a newcomer to town, Stanford Talbot.  He had just moved because his younger brother had told him how friendly and accepting the town was.  Harrison and Stanford talked for a bit, really hitting it off.  Harrison, though he was still angry with his brother, went home to think things through.

When Lionel's new wife, Michelle, moved in, Harrison accepted her...after all, it wasn't her fault his brother was a fickle fool, right?  Besides, now that he had made a new friend--and a friend, besides, who seemed interested in developing it further--he could handle the situation.  Eventually, Stanford invited Harrison to move in with him, and Harrison left the Silver household, taking the name of Talbot for his own.

Harrison remained a Theorist, and his limited income was vital in supporting the two of them because Stanford was working to establish himself in the Paranormal field.  Even after he rose to become an Exorcist, the two had to practice careful budgeting--1870 Simoleons a day don't go very far.  Around this time, Harrison learned that Stanford's younger brother was Ned Smith, and that he was actually the boyfriend of Harrison's own youngest brother Casper, who had been asked to leave the military.

Crystal Talbot, one of Stanford's sisters, moved into town with her son Calvin.  Recently widowed, she was struggling to make ends meet.  Determined to make it on her own, though, she fought hard and became a Fashion Columnist, all on her own merits.  Realizing that Calvin needed a father figure, however, she accepted Stanford's invitation to move in with him and Harrison.  Although reluctant, Crystal decided it was for the best:  Stanford and Harrison could take care of Calvin while she worked evenings, and Harrison was a much better cook than she was anyway.

On the way to work one day, she met Nicholas, a traveler who had stopped over for a little while.  They hit it off, and Nicholas decided to settle in town.  Originally from circus stock, he reconnected with his heritage and found work at the nearby permanent circus grounds.  When their schedules permitted, he and Crystal dated.  Eventually they married and Nicholas moved into the Talbot home.  Shortly after rising to become a Lion Tamer, he and Crystal had a son, Cody.

Although Calvin liked having three fathers, it felt a little weird to have only one mother.  However, shortly before Cody's appearance, Stanford's other younger sister Misty came looking for a place to stay.  Recently divorced from her husband (whom she learned preferred men to women) she had custody of one of their sons, Mickey.  They moved in, and now Calvin had two mothers, three fathers, and counting Mickey and Cody, two brothers as well.

Misty, freed from the burden of raising a child by herself, was able to go back to school and earn a business administration degree.  Now as the CEO of her own company, she contributes to the family income, boosting it considerably.  Now, instead of just Stanford and Harrison's paltry 1870 Simoleons a day, their income was 4645 Simoleons a day.  Now they could afford to really expand their home and enjoy the "wants" instead of just meeting the "needs."

Incidentally, Crystal's husband's death and Misty's ex-husband will be returned to in other families...just to let you know.