{His father and his mother} (ho pat(8872) autou kai h(8820)m(8874)(8872)).
Luke had already used "parents" in  2:27 . He by no means intends
to deny the Virgin Birth of Jesus so plainly stated in  1:34-38 .
He merely employs here the language of ordinary custom. The late
MSS. wrongly read "and Joseph" instead of "his father." {Were
marvelling} ((886e) thaumazontes). The masculine gender includes
the feminine when both are referred to. But (886e) is singular, not
(8873)an, the normal imperfect plural in this periphrastic
imperfect. This is due to the wide space between copula and
participle. The copula (886e) agrees in number with ho pat(8872)
while the participle coming last agrees with both ho pater kai
h(8820)m(8874)(8872) (cf.  Mt 17:3  22:40 ). If one wonders why they
marvelled at Simeon's words after what they had heard from
Gabriel, Elisabeth, and the Shepherds, he should bear in mind
that every parent is astonished and pleased at the fine things
others see in the child. It is a mark of unusual insight for
others to see so much that is obvious to the parent. Simeon's
prophecy had gone beyond the angel's outline and it was
surprising that he should know anything about the child's
destiny.