A general rule for twins is that Mercury, will either be in the ascendant, or in the Seventh House. In the these twins’ chart. it is in its own house Virgo in the 7th house, conjunct with the ruler of the 3rd and 8th house, Venus, which, however, is debilitated.
The twins began their life in a difficult Saturn period, lasting a little less than 8 years. Saturn, itself, is not well positioned in Taurus, which is the 3rd house of talents and artistic development. Saturn is also conjunct (together with) the ruler of the ascendant lord Jupiter, thus also diminishing the Ascendant, which will have control over bodily development. Also, as Venus is the lord of the 3rd house (of talents), it is also diminished, however, Venus is conjunct with strong Mercury moderating That (diminishment). So, there may be some underlying hormonal imbalances.
Since the twins have just entered a new planetary period (Mercury) for 17 years, they are entering a brighter time of their life. Since they began life in a very, very difficult Saturn period of 8 years, I would recommend a reassessment of their autism and a second opinion on medications to see if the meds are still necessary. some parents of autistic children find that a change in diet does wonders (gluten free). Since both Jupiter and Venus are afflicted, diabetes should be ruled out also. Autistic children are not necessarily non-verbal, and, since Saturn is fallen and placed in the area associated with the head and brain, a neurologist should be consulted for interferences with speech and hearing, and sign language as an alternative can be taught to the children, as it is readily learned.