what they see in each other also is difficult to fathom . 
(ROOT (S (SBAR (WHNP (WP what)) (S (NP (PRP they)) (VP (VBP see) (PP (IN in) (NP (DT each) (JJ other)))))) (ADVP (RB also)) (VP (VBZ is) (ADJP (JJ difficult) (SBAR (S (VP (TO to) (VP (VB fathom))))))) (. .)))
(ROOT (S (SBAR (WHNP (WP )) (S (NP (PRP )) (VP (VBP ) (PP (IN ) (NP (DT ) (JJ )))))) (ADVP (RB )) (VP (VBZ ) (ADJP (JJ ) (SBAR (S (VP (TO ) (VP (VB ))))))) (. )))