What is the religious ruling on paying a commission to a broker who informed me of the existence of a customer interested in buying the heirs' house, but did not connect me with him, and then I sold the house to someone else, while I am almost certain that the broker was the reason the buyer found the house, despite there being something that negates this?

If the buyer did not come through the broker, then the broker is not entitled to a commission, because there was no work from him. And if the broker claims that he directed the neighbor to you, and the neighbor denies it, and there is no evidence, then if you believe him, you must pay him the commission from your share only, without the share of the minors or the rest of the heirs, because your acknowledgment against them is not valid, and because acknowledgment is an argument limited to the one who makes it. Disputes are referred to the Shariah judiciary.