I don't see the similarity between Maddie and Cat. Maddie was far too into herself and came across very snotty.
Cat seems down to earth and level headed. With a feisty side if she needs to.
I also don't see the similarity between Tahan and Aisha. I think the comparison first started when people were saying Aisha is the best looking girl in the house, like with Tahan. Tahan was a rat bag. She stirred the pot and didn't care. Tahan was often selfish and loved a good argument.
Aisha seems very Switzerland. I certainly think she is more a Jade than anything else. I think she is very girl next door while Tahan (tho I love her) was more mistress from hell.
Also, assuming housemates are related purely because they are "similar" in my opinion is very naive.
The execs look for 'characters'. People who fit a certain role they are hoping to fill.
Someone loud and boisterous, the girl next door, the few pot plants who will get evicted early, the prankster, the one who loves to argue and debate, someone simple minded and of course a Gay guy, for example.
Each year these roles are filled, they're all going to come across similar to one another. This doesn't mean they're related.
Although of course as we know, it appears a connection to a past HM is some sort of mandatory criteria. But I don't think this has anything to do with reflecting the same 'character'.