Similar chess openings? (d4 defenses compared to e4 defenses)

Hello everybody!

My question is the following: can we find similarity in e4 and d4 defenses? I mean for example the Caro-kann defense compared to slav, the french defense compared to Queen's gambit declined, Pirc opening compared to King's indian defense, and maybe there are same examples what I did not mentioned.
Frenc - QGD

Caro-kann - Slav

Pirc opening - KID

But there are a similar to saemisch line in the pirc as well.

And now in the pirc defense.

So the question is this: Are these openings (and maybe some others I do not know now) very similar to each other in their strategical Ideas, or they are just very similar in moves, but not really the same of their ideas? (I know the pirc and KID are similar to each other, (Or at least white's idea to fight against it) but the others?)

Because if they are similar, then it is easy to have a good repertoire for black mainly.

There are major differences in all of these cases, but some of the ideas are the same. Light square strategies such as the caro slav complex have similar pawn structure and strategic pawn break for example c5 or e5.

I play the Caro and Semi-slav

I have seen so many players try to pair up their defenses this way, and it really is a big mistake to do so as they aren't alike at all except Black's pawn structure.

For example, let's say you are a big fan of the French Defense.  The French is often known for having White pawns on d4 and e5, Black pawns on d5 and e6.  The center is completely BLOCKED, and the theory of pawn pointing takes over, where White's blocked pawns point towards the Kingside, and Black's the Queenside, and so the players should act accordingly.

The Queen's Pawn opening with the biggest similarity to the French is NOT the QGD, but rather, the King's Indian Defense, where once again, you are talking a completely blocked center with White pawns on d5, e4, and f3, Black pawns on d6, e5, and f4, and so with the center blocked, the attack is on the wings, like the French, and Black's pawns point Kingside, White's Queenside, and so the players attack accordingly.

So when you go to compare similar openings, compare which ones lead to similar ideas in the middlegame, not which ones have Black pawns on the same squares.

Like in the example given above, the French Defense and King's Indian Defense feature a lot of similarities, and go hand-in-hand really well.