There is a female and male child. Both eat food and have reached two years of age.
Their urine is impure just like the urine of a grown up.
There is complete agreement among the Jurists regarding this.
When the urine soils a garment it must be washed. The evidence for this is the following hadiith
Narrated Abu Huraira:
Allah’s Messenger (sallallaahu alayhi wa sallam) said: “Beware of (smearing yourselves with) urine, because it is the main cause of punishment in the grave”.
[Reported by Ad-Daraqutni]
Ibn Hajar said it is Sahiih in regards to the chain of narrators.
Abu Haatim said that the raf' (attributing it to the Messenger (sallallaahu alayhi wa sallam)) of this hadiith is baatil.
We have a small female and male child. Both do not eat food. They are in the age where they are breastfed. There urine is impure like the urine of others according to the Hanafi and Maaliki schools of thought in regards to the fact that one has to purify what is soiled by the urine based on the above mentioned hadiith.
The Maalikis have said that if a little of urine or feces of the small child soils the garment or the body of the one who breastfeeds, regardless of if she is the mother or some one else, then it is forgiven provided she did her best to avoid the impurity from soiling her when it came out. However, it is recommended that she washes it.
The Shaafi'i and Hanbali schools have differentiated between the urine of the small female child and small male child.
If a garment is soiled by the urine of a small male child, then sprinkling water on it suffices.
If a garment is soiled by the urine of a small female child, then one must wash the garment.
They base their opinion on the following hadiith
Ubaidullah bin Abdullah bin 'Utba bin Mas'ud said:
Umm Qais, daughter of Mihsan, was among the earliest female emigrants who took the oath of allegiance to the Messenger of Allah (sallallaahu alayhi wa sallam), and she was the sister of 'Ukkasha bin Mihsan, one amongst the sons of Asad bin Khuzaima. He (the narrator) said: She (Umm Qais) told me that she came to the Messenger of Allah (may peace he upon him) with her son and he had not attained the age of eating food. He (the narrator, 'Ubaidullah), said: She told me that her son passed urine in the lap of the Messenger of Allah (sallallaahu alayhi wa sallam). The Messenger of Allah (sallallaahu alayhi wa sallam) sent for water and sprayed it over his garment (over that part which was contaminated with the urine of the child) and he did not wash it thoroughly.
Abu Al-Samh said:
"The Prophet (sallallaahu alayhi wa sallam) said: 'A girl's urine should be washed away and a boy's urine should be sprinkled with water.'"
Everything that has been mentioned of the agreement of the Jurists and their disagreement regarding the urine of a small male and female child also applies to the vomit of the small male and female child.
Kuwaiti Encyclopedia of Fiqh
Volume 27 Page 25-26