legitimise vs legitimate

legitimise is not an adjective while legitimate is an adjective.

Word	Noun	Adjective	Verb	Adverb
legitimise	No	No	Yes	No
legitimate	No	Yes	Yes	No

As verbs, legitimise and legitimate are synonyms defined as:

Other synonyms of legitimise include decriminalise, decriminalize, legalise, legalize, legitimatise, legitimatize, legitimize.

legitimise (adjective)	legitimate (adjective)
	of marriages and offspring; recognized as lawful
	in accordance with recognized or accepted standards or principles
	authorized, sanctioned by, or in accordance with law
	based on known statements or events or conditions

legitimise (verb)	legitimate (verb)
make legal	make (an illegitimate child) legitimate; declare the legitimacy of (someone)
	show or affirm to be just and legitimate
	make legal