All I really had to go on for Keen’s sister was the lyric from the song You’ve Got to Eat Your Vegetables where Keen’s sister says, “You’ve got to eat your vegetables.. Na-na-na-na-na-na!” so that’s where I got this one from.
On a related note, I’m going to be tackling Keen’s brother a few strips down the road, but I haven’t been able to find an official name for him. I saw in the wiki that one fan-fiction had him as “Bobby,” but that’s too close to my name so I’m just not going there. I was just going to go with “Tom,” but if anyone knows something closer to canon, just let me know.