== On his marriage to Elvira de Monzón == 

 There is no record that Elvira married Ladrón.  She married count Rodrigo Gómez (Salvadorez) and appears with him in Oña in 1142 and he died in 1160. In 1161 she appears in Oña confirming the donations made by her late husband. She is said to have died in Jerusalem and her body brought back to Oña for burial. So it seems unlikely that she married Ladron who appears in two charters in 1149 making a donation with his wife Teresa (Historia del condado de Oñate y señorío de los Guevara (...) by María Roasa Ayerbe Iríbar - 1985, pag. 12). THe term princeps or similar in early navarrese charters appears often but does not refer to a "prince" per se, but rather to a "principal" character, a sennior.