I think he would be 60 now...

[NAL123]

Suppose I'm speaking to my friend whose father died a few years ago.

(1) Me: Today is your father's birthday! I think he would be 60 now?
(2) Me: Today is your father's birthday! I think he might be 60 now?

In both (1) and (2), the implied condition is "if he were alive now".

Question: Are (1) and (2) correct with "would" and "might"? Or do we need the perfect forms: would have been and might have been?

 

[emsr2d2]

Suppose I'm speaking to my friend whose father died a few years ago.

(1) Me: Today is your father's birthday! I think he would be 60 now.
(2) Me: Today is your father's birthday! I think he might be 60 now.

In both (1) and (2), the implied condition is "if he were alive now".

Question: Are (1) and (2) correct with "would" and "might" no question mark here or do we need the perfect forms no colon here would have been and might have been?

Note my changes above. Don't start a sentence with "or". The second sentence in both 1 and 2 isn't a question.
"Would" works but "might" doesn't. The first is a statement of fact, and it is a fact. The second fails because if he were alive, we couldn't say "he might be 60 today" so you can't say it with the conditional either.

I'd probably say "It would have been your dad's 60th birthday today!"

 

[NAL123]

The second fails because if he were alive, we couldn't say "he might be 60 today" so you can't say it with the conditional either.

Do you mean to say in the following counterfactual second conditional

If he were alive, he might be 60 today.

"might" is grammatically correct and might be used in a similar counterfactual second conditional in a different context, but the reason why it doesn't work in the sentence above is that it doesn't make sense there?

Consider:

If my friend were still alive, he might still be living next door. (That is, he might not have moved house)

 

[emsr2d2]

If he were alive, he might be 60 today.

That doesn't make sense. If you know it's his birthday, and you know he was born 60 years ago, then he would be 60 today. A lot of things might be true today if he were still alive - he might have sailed around the world, he might have learned how to fly, he might have divorced and remarried fifteen times, he might have decided to go and live in the Australian outback, and many other possibilities. You get the picture. All of those things are "might have beens". The simple fact is that if he had not died, he would be 60 today.

If my friend were still alive, he might still be living next door. (That is, he might not have moved house.)

That's fine. It's one of an infinite number of possibilities that might have come true if that friend were still alive.