(1) I always laugh at my brother's jokes even though they are never funny. (concessive)
(2) I always laugh at my brother's jokes even if they are never funny. (conditional)
You've asked an interesting question. If you’re asking whether they are interchangeable with no change in meaning, the answer is yes, possibly, depending on the intended meaning.
There is quite a close relation between "even though" which is primarily concessive, and "even if", which is primarily conditional. Of course, both sentences entail that you always laugh at your brother’s jokes, but typically there is difference in both the meaning and grammar of the subordinate clauses.
(1) says that your brother’s jokes are never funny (but I laugh at them nevertheless), while (2) leaves it open as to whether his jokes are funny (but I laugh at them whether they are funny or not).
BUT, and this is what I think you’re getting at: there is a context where the complement of "if" is known to be true, for example:
(3) You don’t have to defend everything Ed does, even if he is your brother.
In that example, there is no doubt that Ed is your brother, so that the conditional is equivalent to the concessive "even though".
So yes, it’s possible depending on context, i.e. the intended meaning.