okay so their mom is a korean immigrant who moved to the states with her first husband. they had 3 kids together (joy, peter, and grace). her first husband was not thrilled about a third child and shortly after grace turned one he took off. he moved back to korea and married his ex gf. martha finished up a degree in nursing and began working at a local hospital. on her first day she met a very handsome doctor who was also a single parent and had two kids. they began dating and within six months of meeting they married. sydney pb would be their daughter together and she is the youngest of the bunch. they are boston natives and grew up in an upper middle class neighborhood with a big backyard. the parents were very adamant that the kids all do well in school and behave and they are all extremely tight knit. the stepfather basically raised the three cho kids as his own and there's no half or step siblings in the family; they're all just siblings. i've said that grace and her sister fought a little (grace was slightly miffed that she was replaced as the youngest and cutest) but she still loves her sister and would do anything for her.