Breeding
Take a look at the image down below to get an idea of what differentiates a male from a female. The genitalia can be examined to determine the gender of the animal.
The average amount of time  between births is approximately 151  and 156 days. There is  a range of 140 to  146 days for the gestation  period. They begin to become  less active in the few  weeks leading up to the  birth. When they are giving  birth, you should not bother  them in any way. In  most cases, it will take  place in the evening. The  actual delivery takes about sixty  minutes. The beginning of labor  is determined by the time  that the first young can  detect the beginning of contractions.  The time that elapses between  each infant is typically between two and  five minutes. The afterbirth typically  occurs ten to thirty minutes  after the delivery of the  final young and is consumed  by the female as well  as other members of the  social group. If the labor  is taking too long, you  should seek the advice of  your veterinarian (caesarian can save  the female). They typically have  two children at a time.  There are times when one,  two, or three monkeys are  born. In most cases, if  a mother gives birth to three children, one  of those children will pass  away within the first week  after birth. It is possible  that one of the three  needs to be reared by  hand. Do not underestimate the  difficulty of the task at  hand; HAND-REARING is not a  simple job. Everyone in the  family takes turns carrying the  newborns. They will occasionally hand  the infants back to the  mother so that she can  continue to nurse them. After  30 days, the newborns will  begin to show some interest  in food.
When the infants have reached  the age of 40 days,  they are able to make  it on solid food and  milk substitutes.
Suckling typically lasts for about  a hundred days.
At the age of six  months, the marmosets are old  enough to be weaned completely.  By this time, the breeding  female has typically given birth  to another litter, and the  subadults have begun to learn  how to care for themselves.
Marmosets reach sexual maturity between  15 and 18 months after  birth.
In captivity, marmosets can live anywhere  from 7 to 20 years.
Handrearing
Marmosets are capable of giving  birth to more than two  monkeys on occasion. The fact  that the mother can only  properly care for two infants at  a time usually results in  the rest of the monkeys  passing away within the first  week of their lives. It  is possible that one of  them will need to be  manually reared in order to  stop this from happening.
Hand-rearing is not a simple  task, so make sure you  don’t undervalue its difficulty.
During the first three weeks  of their lives, the young  animals need to be given  a protein multivitamin concentrate and  powdered human milk substitute every  two hours, from 8:00 to  24:00. Mix one teaspoon of  glucose with 28 milliliters of  sterile water for the first  feeding (give only 0.3-0.5ml). After  the first three weeks, you  can gradually introduce baby cereal  into their diet.
Example 1: Rearrange your hands  according to the schedule
Example 2: Rearing of the  hand – on the timetable!!!  You might want to think  about giving them Primilac as  an alternative to artificial milk  or human milk substitute. This  is a non-human primate milk  replacement product!!!
After each feeding, gently massage the anal  region with cotton wool that  has been soaked in baby  oil. This is necessary in  order to maintain the moisture  level of the anal skin.
Infants should be kept in  a wooden nest box at  a temperature between 25 and  28 degrees Celsius (humidity at  50 percent ).
Provide the child with a  “artificial mother” so that they  can cling to it (like  a towel).
After one week, you should  administer 1 drop of vitamin  D3 to your monkey twice  per week.
Growth
Newborn : Normally born with  eyes open.
Head and body : 60-80mm, weight :  30g
Body covered with fine gray  hair, tail with dark and  grayish bands.
Ear tufts absent.
2nd Week : Able to  crawl unsupported
3rd Week : Starts to  take some solid food from  parents
4th Week : Leave parents  from time to time.
5th Week : Lap liquids.
6th Week : Head and  body : 120 – 50  mm, weight : 70g Milk  dentition complete, If necessary they  can survive on solid food  and milk substitutes
7th Week : Weight :  80g
8th Week : Head and  body : 140-70mm – weight  : 91g
9th Week : Weight :  97 g
10th Week : Weight :  103 g
11th Week : Small ear  tufts become visible (dark gray).  Weight : 105 g
12th Week : Independent of  parental care.
14th Week : Ear tufts  becoming silvery.
Suckling ended.
17th Week : Weight :  137 g
20th Week : No longer  on adult back.
22th Week : Weight :  166 g
28th Week : White ear  tufts
Weight : 174 g 60th  Week :
Full sexual maturity reached.
