many a boy and many a girl

许多人

“many a＋单数可数名词”形式上为单数，但意义上为复数(意为“许多”)，若用作主语，其谓语通常与形式一致而不与意义一致(即谓语用单数)。如：
Many a student has seen the film. 许多学生看过这部电影。
Many a fine man has died in that battle. 许多优秀的士兵死于那次战役。
Many a ship has been wrecked on those rocks. 许多船只毁于那些礁石之上。
Many a young man has tried and failed. 很多年轻人都试过，而且失败了。
Many a successful store has paid its rent cheerfully. 许多成功的店铺都非常乐意地付了房租。
注：“many a＋单数名词”是一个十分正式的结构，在口语或非正式文体中一般都用 many＋复数名词”代之。

Many
a
young
man
has
tried
and
failed.
很多年轻人都试过，而且失败了。
Many
a
successful
store
has
paid
its
rent
cheerfully.
许多成功的店铺都非常乐意地付了房租.
许多船只毁于那些礁石之上.
许多优秀的士兵死于那次战役。
Many
a
ship
has
been
wrecked
on
those
rocks许多人
“many
a＋单数可数名词”形式上为单数，但意义上为复数(意为“许多”)，若用作主语，其谓语通常与形式一致而不与意义一致(即谓语用单数)。如：
Many
a
student
has
seen
the
film.
许多学生看过这部电影。
Many
a
fine
man
has
died
in
that
battle

一个是单数
两个就是复数了
这个没有疑问

and 连接两个名词时，如果名词前面有many a,no,each等修饰，谓语动词用单数。

一个有一个的男孩和一个有一个的女孩