substitute for chickpeas in "bean blondies" I'm trying to make "chickpea blondies" However, my brothers won't eat them because chickpeas are estrogenic.

In the recipe, you have to puree the chickpeas, add some peanut butter for strength and taste, and then bake it. So it needs to be relatively firm, sweet or nutty, and hold up in heat. . Is there some other sort of firm bean/food item that could be substituted for the chickpea? They don't have to be beans. I've seen avocados used in recipes like this, but one brother is allergic

Please don't say flour, because making actual brownies defeats the purpose. The fun of it comes from making an  tasty imitation dessert out of unconventional non-dessert ingredients like *beans. 

*excepting red beans
I've had great success with black bean brownies. Most recently I tried this recipe on recommendation from a friend and it turned out quite well! Very rich, great-textured brownies.

The batter is quite thick, though, so make sure your blender/food processor is up to the task!