[Oztrich Boy]

You might want to look up the word "legitimate" in a dictionary some time

legitimate, le-jlt'-te-mate a. born in marriage (Samuel Johnson, A Dictionary of the English Language, 1755)

The Shorter OED gives a second meaning of "conformable to law or rule; lawful, proper".
It also notes that it was sometime used in a transferred sense of "real" as opposed to "spuriuous". but notes that usage as obsolete.

[Diamond]

Webster's 1828:

legitimate

LEGIT'IMATE, a. [L. legitimus, from lex, law.]

1. Lawfully begotten or born; born in wedlock; as legitimate heirs or children.

2. Genuine; real; proceeding from a pure source; not false or spurious; as legitimate arguments or inferences.

I guess Mirriam-Webster and John Grishmam, et al didn't get the OED memo that the 'not spurious' sense is obsolete

Definition of LEGITIMATE

1

a : lawfully begotten; specifically : born in wedlock b : having full filial rights and obligations by birth <a legitimate child>

2

: being exactly as purposed : neither spurious nor false <a legitimate grievance> <a legitimate practitioner>

3

a : accordant with law or with established legal forms and requirements <a legitimate government> b : ruling by or based on the strict principle of hereditary right <a legitimate king>

4

: conforming to recognized principles or accepted rules and standards <a legitimate advertising expenditure> <a legitimate inference>

5

: relating to plays acted by professional actors but not including revues, burlesque, or some forms of musical comedy <the legitimate theater>

Examples of LEGITIMATE

1. legitimate means for achieving success
2. the legitimate use of firearms
3. There's no legitimate reason for prescribing this medication to a child.
4. Law books were getting thicker by the week with Supreme Court decisions barring legitimate claims because they weren't timely filed. —John Grisham, The Chamber, 1995
5. Even in many courtrooms, where there is valid concern about the privacy of defendants, judges recognize that camera coverage serves a legitimate public interest. —New Republic, 22 Feb. 1993
6. He was indeed already a legitimate child according to the law of Scotland, by the subsequent marriage of his parents. —Sir Walter Scott, The Heart of Mid-Lothian, 1818

Cordially,