Some infectious diseases of course are contagious or perhaps both are exposed to the same thing causing the illness eg mosquito bites causing Malaria. However DO NOT TREAT A CHILD IN ANTICIPATION!! Always wait and then see a doctor! Never assume it is the same illness. You may be wrong! It is also not automatic that the child will be sick at all

You will likely have to see a pedodontist (commonly called a pediatric dentist) who specializes in children's dental care

You can see Babymigo Children dental developmental chart below;

https://www.instagram.com/p/CS1H1dDD9C8/

More than 70% pregnant women find out their baby's sex during ultrasound, which is usually done between 16 and 20 weeks. I wish you all the best

Walking on tiptoes can be normal variation especially if other members of the family also walk on tiptoes growing up. It can also be a sign of neurological disorders. If you are really worried kindly see a Paediatrician for thorough evaluation first

The only one I'm aware of is the Chinese method. Check Google. I also find this help one here helpful https://www.huggies.com.au/childbirth/multiple-births/twins/how-to. All the best

Try giving them a multivitamin

Natural, I don't know if there is a specific method o. Your best bet is IVF

It's true for some and false for others. It's depends on a lot of things like position of placenta, position of babies,e.t.c. above all your doctor would be in the best position to dictate what will happen