1. 
[syn: legitimately, lawfully, licitly]
2.  in a lawfully recognized manner; 
- Example: "let's get married so our child can be born legitimately"
The Collaborative International Dictionary of English v.0.48:
Legitimately \Le*git"i*mate*ly\ (-m[asl]t*l[y^]), adv.
   In a legitimate manner; lawfully; genuinely.
   [1913 Webster]
WordNet (r) 3.0 (2006):
legitimately
    adv 1: in a manner acceptable to common custom; "you cannot do
           this legitimately!" [syn: legitimately, lawfully,
           licitly] [ant: illegally, illegitimately,
           illicitly, lawlessly]
    2: in a lawfully recognized manner; "let's get married so our
       child can be born legitimately" [ant: illegitimately, out
       of wedlock]