Hi! i used to have the same info that you now have, bout someone corrected me that my Pedro Ycazbalceta y Uriarte (who i had as a brother of your Juan Ycazbalceta) was actually called Pedro de Ycazbalceta y Sologure son of Francisco de Ycazbalceta and Maria Martinez de Sologuren!he later married Maria de Texeria no Maria Saez Marque as i thought and was the father of Juan Francisco de Ycazbalceta y Texería married to Catalina de Extebarria, who i actually had in my data!, al this was elegedly taken out of the actual documents, so, i think the info i sto be trusted.. but i found someone who has the same info you have: http://gw.geneanet.org/index.php3?b=jpchac&lang=en;p=jua... maybe it'll help you...
but you know? Icazbalceta is such a rare name that we're probabbly related anyway, but i'll need to keep searching how... Maybe my Francisco Ycazbalceta who married Maria Martinez de Sologuren, was the brother of your Pedro de Ycazbalceta y Perez-Goitia!...
I'll save you'r email to send you anything i can ok?..
Regards,
Mauricio