I have seen people try to blend their voices with others and do damage to them. The notion of "blend" in itself is not instructive.
The great choruses such as fine gospel singers or Robert Shaw chorale balance the voices. There are ways in which distinct voices can learn to sing together and retain their own structural integrity and not degenerate into a "mushy" or affected sound.

As to what people will tell you, you can't always gauge what's going on by that. People can be often as wrong as they appear to be right. I would trust a good vocal teacher more than any offhand comment well-meaning friends might make. Anyway, I've made my point and that's it for me.

Frank Hamilton.