In The Westing Game what was Sam Westings motive?

He wanted to forgive Crow for making his daughter kill herself because Crow wanted her to marry a man she didn't want to. So basically, to forgive Crow.

That was not the only motive..

Sam Westing paired the people the way he did in the book because he wanted to help everybody. For example, Turtle did not have a good relation with her mother. By pairing Turtle with Flora, Turtle gained a "second mother". Flora also benefited from this because her daughter had died, and she had nobody to take care of. Every single partnership went this way, and in the end, everyone was happy.