Common, survivable, and largely determined by what the two of you agree in advance rather than by what your parents do.
Work out what it actually is
Four different situations get described the same way, and they need different responses.
They simply have nothing in common. Different backgrounds, different money, different noise level. Not a problem, just an absence. These families need to be in a room together a handful of times a year and that is fine.
One family disapproves of the marriage. Different, and harder.
Specific friction over something concrete. Wedding costs, custom, who was not consulted. Usually solvable, because it is about a thing rather than about people.
One family behaves badly toward the other. The serious version, and the one that requires the couple to take a position.
Being precise about which you have saves a lot of wasted effort.
The agreements that carry most of the weight
You are the unit. This has to be settled between the two of you before it is tested. When a family and the marriage want different things, the marriage decides. Saying this in principle is easy; holding it when your own mother is upset is not, and that is the actual test.
Each of you handles your own family. Always. A partner defending themselves to their in-laws without their spouse having spoken first is a pattern that ends with them saying nothing at all.
You do not have to fix it. Two families being polite a few times a year is an acceptable outcome. A great many couples exhaust themselves trying to engineer a friendship that neither set of parents wants.
Keep them apart where you can. Separate celebrations, separate visits, one shared occasion a year. This is not failure. It is competent management.
The wedding
The pressure point, because it forces both families into one room, one budget and one set of customs.
What helps: decide the substance as a couple first, then inform rather than consult. Be clear about who is paying for what and what that does or does not buy in terms of say. And where the friction is about custom — whose melodies, whose traditions, which rabbi — name it as custom, and choose deliberately rather than letting the louder family win by default.
Where an actual halachic question is involved in what the wedding requires, take it to a rabbi rather than settling it between the families. It stops being an argument about whose side is right.
If one family disapproves of the marriage
Two questions, in order.
Is any of it worth hearing? Occasionally a parent is seeing something real that you are not. It costs little to ask yourself honestly, once.
If it never changes, are you each prepared to marry anyway? Say it out loud to each other. Couples who have not said it tend to find out the answer at the worst possible moment, usually with one of them discovering that the other was privately waiting for approval that was never coming.
Where the disapproval is about background, community, or level of observance, it is worth separating a family’s genuine concern from prejudice they have inherited. Both exist in Jewish families. They warrant different amounts of patience.
What not to do
Do not relay criticism between families. Do not make your partner the messenger to your parents. Do not keep a private ledger of which family has behaved worse. And do not assume grandchildren will solve it — sometimes they help, and sometimes they add a new front.
The long view
Most couples in this situation report that it mattered enormously for about two years and then settled into a manageable background condition. What determined whether it settled was almost never the parents. It was whether the couple presented a single position.
If the same argument keeps recurring between the two of you, that is the thing to address — and that is what Marriage Reset coaching is for.