Bukhari

Hadith Commentary:
At that moment, my doubt was removed.
The name of Usamah's mother is Umm Ayman, who was the freed slave woman of your (the Prophet's) father, Abdullah, and she played a significant role in the upbringing of the Messenger of Allah (sallallahu alayhi wa sallam).
Usamah was your (the Prophet's) freed and very beloved, almost like a son. At the time of the Prophet's (sallallahu alayhi wa sallam) passing, his age was twenty years.
He passed away in the year 54 AH, (radi Allahu anhu).

Hadith Commentary:
(1)
There is a difficulty in this hadith: How could the Messenger of Allah (sallallahu alayhi wa sallam) seat both Usamah (radi Allahu anhu) and Hasan (radi Allahu anhu) on his thighs at the same time, when at the time of the Prophet’s (sallallahu alayhi wa sallam) passing, Hasan (radi Allahu anhu) was eight years old, while Usamah (radi Allahu anhu) was a young man during the Prophet’s (sallallahu alayhi wa sallam) blessed life? The Prophet (sallallahu alayhi wa sallam) had, during his lifetime, appointed Usamah (radi Allahu anhu) as the commander of an army in which a large number of the noble Companions (radi Allahu anhum) were present.

It is possible that the Messenger of Allah (sallallahu alayhi wa sallam) seated both at a time when Usamah (radi Allahu anhu) was still youthful and Hasan (radi Allahu anhu) was around two years old, or that the Messenger of Allah (sallallahu alayhi wa sallam) seated Usamah (radi Allahu anhu) in his lap due to some illness, and during that time also seated Hasan (radi Allahu anhu) on his other thigh.

(Fath al-Bari: 10/534) (2)
In any case, due to love and affection, seating children on the thigh is permissible; there is no kind of insult or disrespect in this.