Before Birth
It is known that male aliens like Pollination Technician can impregnate male Sims. But Lola had no clue she could impregnate woman and... herself! She was shocked and thrilled at the same time. Her sister Chloe, now aware of this impregnated her partner Erin Beaker with succes, as she thought a pregnancy must be awful to deal with.
Babyhood
When Tessa was born it was clear by her brown hair that Kristen Loste was her other parent, what made sense as Lola and Kristen are married.
Teenhood
Tessa always knew she was different, but she also knew she wasn't the only one. She met the three Curious cousins in High School and she fell in love with Lucifer Curious, he answered her love and they starting dating. Both of them nor their parents were aware that they are actually 'half-cousins', as in Pascal, Vidcund and Lazlo are actually half-brothers of Lola and Chloe. The only person who could know was their human father Glarn Curious but he was already deceased before Lucifer was even born.
Adulthood
Tessa is a few days younger than Lucifer so she was happy when she finally grew up and could move in with him to start their own family. Moving in the Curious household it is already a crowded place although Pascal, Vidcund and Lazlo recently moved out. There was already a new baby born, her grandnephew Drew and the later to be known grandniece Sarah was on her way.
In the mean time she creates a pretty good friendship with her 'cousins-in-law' partner's Marsha and River
Lucifer and Tessa decided to take things slow and just get engaged for a while.
When Klatu and Marsha with their son Drew moved out due some relationship problems Lucifer and Tessa got married and shared their first WooHoo after their marriage(!) hoping for their first pregnancy.
It seems that Tessa got pregnant very fast and gave after the normal 3 days of pregnancy birth to TWINS! Two boys named Lucas (the oldest) and Joshua Curious