I'm not sure which Ignacio Pesqueira you are looking for - the famous General Ignacio Pesqueira, Governor of Sonora, has descendants all over Sonora. Many are concentrated in Arizpe but folks out there don't have Internet or email yet. You might drop a line to Ignacio and Silvia Pesqueira, Arizpe, Sonora Mexico. They have the whole family pretty much charted out. They speak only Spanish, but a bunch of us will be down there the first part of May and could read your letter to them.