Hi Eliza_Nara!
I am a user of the Version 4.5 myself and I have experienced something similar to what you have twice. By any chance, does your Ura Memetchi have high Glamour/Gorgeous points (The middle icon in the skill points with the sparkle)? I found that if a teenage Tama has a high number of points in a certain category (At least 160 I've found), then they tend to switch families when they evolve into an adult.
Just recently, I raised a male on my Version 4.5, and he became a Kujakutchi for his teenager stage (A character in the Ura Meme family). However, I gave him a high number of Funny/Humour points and by the time he was to become an adult, he had 164. Due to this, he evolved into an Ura Mametchi, switching families from Ura Meme to Ura Mame as a result! I since raised his Humour points some more and he is currently the secret character Hyottokotchi.
This trick is something that I personally call the "Family Switch Trick". It seems that unlike the Version 4, you can have a Tama change families from the teenager to adult stages if you have a high number of points in a certain category on the Version 4.5. Due to this trick, I find the Version 4.5's growth chart very interesting, and I plan to gradually conduct experiments in the future! Whether this "Family Switch Trick" is a glitch or not is unknown, but I certainly like harnessing it! It certainly gives the user more freedom in which character they can get.
I hope my help was of use to you!
Hohotchi-HO7
