If an ABC or American says: you brought me to this world,

it's your responsibility to raise me, but when you are old, it's not my responsibility to take care of you. it will be a little easier to understand. But my sister-in-law was born and raised in China, and did not come to the U.S. until 23 yrs old. Unbelievable!

As for "your mom is not my mom", even my American co-workers said: no, you are not only married your partner, you are married his family too.