Can my husband's son fight for inheritance share when we have a legal drawn will by a attorney leaving each other everything?

Where? The son's age does not matter.

Also - has your husband died?
And do you mean you each have wills? One will wouldn't make sense.

Certainly he can fight you. Whether he would win a fight depends on how good your attorney was in drawing up the will. .

If the will is legal the son would have a hard time winning unless he can show that his father was under duress or was incompetent when he signed the will.