Please describe the wheels you are talking about. Are you talking about wheels on the bike or on the trailer? What size rims and how many spokes?

Once you break two or three spokes, your wheel has no hope. That's because the breakages are caused by metal fatigue, and you are sure to break more spokes. The solution to this is to rebuild the wheel with all new spokes. Replacing them one at a time will not do the trick. The completed wheel should have high and even tension.