Breakdown of Il mio nipotino è un discendente di una nobile stirpe.
essere
to be
un
a / an (masculine)
una
a / an (feminine)
di
of, from
Questions & Answers about Il mio nipotino è un discendente di una nobile stirpe.
Why do we use the article Il before mio nipotino? Shouldn't singular family members drop the article with possessives?
You are right that singular family members normally drop the definite article, like in mio nipote. However, this rule has an exception: when the family member's noun is modified by an altering suffix like a diminutive (here, -ino for little), the article comes back. So, it must be il mio nipotino.
Can nipotino mean little nephew as well as little grandson?
Why does the adjective nobile come before the noun stirpe instead of after?
How can I tell if a noun ending in -e like stirpe is masculine or feminine here?
You can spot its gender by looking at the indefinite article una, which tells us that stirpe is feminine. Many elevated or collective nouns ending in -e are feminine, though you always have to memorize them or check the articles around them.