below might be spoilers but idk its just a theory
I was rewatching some klk trying to find out why Tsumugu(red mohawk dude) had the same color hair as Ryuko. I rewatched ep 5, the first ep he appears in to see if I could find any clues. The one thing I did notice was that he was able to hear Senketsu's voice when he said "Don't you dare lay a finger on Ryuko. Do, and I'll make you pay". Then I remembered that Aikuro(blue haired guy) said that Senketsu's life fibers had been spliced with Ryuko's central nervous system's DNA, which is why he can only be heard and worn by Ryuko. So the only possible way Tsumugu was able to hear Senketsu IS HIM AND RYUKO ARE RELATED. Now I'm not saying he's her dad or anything like that.
In ep 17, it is revealed that Tsumugu had a sister who was a lab assistant and the tester of prototype Senketsu. I thought, "Why would they choose her to test it? Why not anyone else?" Obviously it had to be someone related,
LIKE HER MOTHERRyuko and Ragyo share no resemblance

All the times Kinue has been shown(rarely) her face is always concealed. What's the point to hide a mere side character if there's no reason too? Also there is some resemblence.

even with few scenes with kinue it is obvious they have some similarities.
TL;DR I call bullstuff on Ragyo's claim to be Ryuko's mother and that Trigger is loving with us for the umpteenth time.