There's more to you and your brothers than it at first seems apparent to the eye.

There's more to you and your brothers than it at first seems apparent to the eye.
 

-There's more to you and your brothers than it at first seems apparent to the eye.

At the time the speaker speaks this line, the act of seeming should be in the past, why not SEEMED but SEEMS?

I would agree that 'seemed apparent' better captures the meaning.

Simplified:
There's more to you than at first seemed apparent.

The phrase 'at first' calls for the past tense form.

But it can be used in the present too. Right Rusty?

Correct! It depends on what you're trying to say.
If you're referring to the past, you'd use 'seemed'.
If I'm talking about the present, I can certainly say "There's more to you than at first seems apparent."

Thank you. It reminded me of the transformers back in the 80's (cartoons) ;)

But even referring to the present, didn't SEEM still happen in the past?

Not necessarily. Seeming can persist. 'It seemed' can progress to 'it seems' and 'will seem' in the future.
It depends on what you're trying to say.

Thank you, Rusty. But isn't AT FRIST a past time phrase?

No, 'at first' can be used with a present tense verb as well as with a past tense verb.

Or any other tense...

Thank you, Rusty.

But when does/did this SEEM take place if not in the past?

"When you look at it for the first time" --That's a present. ;)

What is your native language?
:)