Yes, "My cousin thinks he was lucky to get into his favorite college" is a simple sentence, not a compound sentence. A compound sentence consists of two independent clauses joined by a coordinating conjunction. In this case, the sentence contains only one independent clause.
The nouns in the sentence "Their daughter Mary is your favorite cousin" are "daughter," "Mary" (a proper noun), and "cousin."
The compound nouns in the sentence are:contact lensshag rugbedroom
Words have plural forms, but sentences don't. It doesn't really mean anything to say, what is the plural form of that sentence. However, the sentence does contain two nouns, sister and cousin, which could be changed to plural nouns, sisters and cousins. It is not necessary to change college, since "in college" does not necessarily mean in a specific college, just in some college.
Melvina wrote about her mother's aunt, and Leroy wrotr about his cousin from Jamaica.
The predicate of this sentence is "is my friend's cousin".
The pronoun for Andrew is he for a subject and him for an object of a sentence; for example:Andrew is my cousin. He attends the community college. I can ask him to the picnic.
i have a lot of cousin
The predicate of this sentence is "is my friend's cousin".
My cousin is very nice
The predicate of this sentence is "is my friend's cousin".
The predicate of this sentence is "is my friend's cousin".
The predicate of this sentence is "is my friend's cousin".