his sister was a late-in-life oops!baby for their parents. full name margaret, typically went by mags or magpie because she loved anything sparkly. she used to make her own jewelry to sell on etsy.
the adolescent crush is a cute addition to their backstory. he probably wasn't oblivious but kindly pretended to be so they could avoid awkwardness. settling into a pseudo-big brother role would have come as a relief. cliff would have been quick to accept her as part of the family back then, but she may find he's more resistant to the idea by now. he feels responsible for too many loses and worries if people are too dependent on him, it's going to end in disaster.