You are better off going with two openings that have a similar strategy, not a similar pawn structure.
This is a very common, flawed idea that amateurs think will work. It doesn't!
Case in point: Take the Pirc, French, and King's Indian Defense
People will say that the Pirc and King's Indian are similar because Black has the same pawn structure in both openings.
Here's the problem with that. BLACK has the same pawn structure. THE BOARD DOES NOT have the same pawn structure. Black can and often does play ...b5 in the Pirc. Other than in Panno lines against the Fianchetto or Saemisch lines, ...b5 is almost non-existent in the King's Indian.
You should be playing two openings that have the same basic ideas behind them:
FRENCH AND KING'S INDIAN! Both openings feature "blocked centers" in the vast majority of variations. Yes, both have exceptions - Exchange French - Four Pawns Attack vs the King's Indian - but the vast majority of the time, the center is not just closed, but BLOCKED in both openings, and the idea is exactly the same in both. Attack the side of the board in which your pawns point. In the French, White's pawns point towards the Kingside, Black's the Queenside, and so White should attack Kingside and Black Queenside. In the case of the King's Indian, White's pawns point towards the Queenside, and Black's the Kingside. Therefore, White should go for a Queenside attack and Black a Kingside attack (look at any game in the Classical Variation and you'll notice that exact strategy over 90% of the time).
Other pairs of openings with similar ideas:
CLOSED RUY LOPEZ (7...d6, not 7...O-O) and QUEEN'S GAMBIT DECLINED - Both feature what is called a "strong point" for Black. It's d5 in the QGD, e5 in the Ruy Lopez. Both feature semi-closed positions that are very strategic in nature.
CARO-KANN and NIMZO-INDIAN - Both feature very fluid positions. A common theme in both is surrendering control of one square in order to gain a bind on another square - typically central squares. Notice how, unlike say, the French, where Black almost always attacks the d4-pawn, the Caro-Kann might feature a bind by Black on e5 in one game, and a bind on e4 in another, or d4, or d5. Within the course of the game, Black may weaken his control over d5 in order to dominate d4, just to give an example. The same thing often happens in the Nimzo-Indian. You surrender e4 to go for c4 or vice versa. Neither opening has one fixed pawn structure like the French and King's Indian do.
SICILIAN NAJDORF OR DRAGON and GRUNFELD - Both are openings that require a heavy amount of imaginative play by Black, both require deep tactical calculation skills, and both tend to be high-risk, high-reward openings with a lower draw ratio. The King is almost never safe in either opening.
So I would recommend looking for two openings with similar strategic ideas and goals rather than a similar pawn structure on HALF of the board! The fact that the other half of the board's pawns are not the same makes lightyears of a difference in the position. Saying that 2 openings are similar because Black's pawns are the same is like saying that the Green Bay Packers going against the Cleveland Browns is the same as the Green Bay Packers going against the New England Patriots because Green Bay used the same 11 players and the same defensive schemes in both games.
By the way, given that you sound like you are looking for something simpler and not loaded with theory, the last one is not a good idea. The Najdorf, Dragon, and Grunfeld all require knowledge of very dense theory and a strong will with the willingness to sacrifice frequently.
I would suggest one of the other 3 pairs in your case, depending on style of play. If you like blocked positions where play mostly takes place on the flanks, go with the French and King's Indian. If you prefer to defend around a strong point, play the QGD and Ruy Lopez. If you think more from a control perspective rather than an attack/defense perspective, like total domination of a key central square with few tactics (not saying there are none, just simply fewer), go Caro-Kann and Nimzo-Indian.
Can't settle on an opening for black. Just returned to chess after decades away. My chess.com on-line rating is just under 1500. I'm happy with my white for 2016. But black? I've abandoned my dabbling with those b6-g6 stuff. I want to return to the center.
Showing potential is 1.d4 slav + 1.e4 Scandinavian. I want a general purpose pair that are similar in pattern of play hence slav-scan. What other combos are around for a lower-level player that are similar to each other. I don't have the patience to study chess like you young fellows.
I just want to play for enjoyment & feel content with a basic black repetoire to learn & stick with plz.