What is the possibility of having twins if both parents are twins?
That depends. Is your wife a fraternal or identical twin? (Identicals are purely by chance and will not influence your ability to have twins!) Being a female fraternal twin increases the chance of having twins as long as she was conceived without fertility treatments. A male being a fraternal twin has no influence on his partner's ability to release two eggs however he can pass the gene on to his offspring. So your female children would definitely have a possibility of having twins and you can pass it to your male children who will pass it to their children, which is why twins can appear to skip generations. In general a person's chance of having twins is about 1 in 80 and it can jump as high as 1 in 17 if you are (or in this case your wife is) a female fraternal twin!
If both parents have big noses, will their children inherit a big nose?
Not necessarily. I have an average sized nose and my husband has a larger nose. On each side my children have one grandparent with a large nose (grandpas), and one with a small to average nose (grandmas). My son got my nose, my daughter (go figure) has a nose shaped like mine but more the size of her daddy's. Both of my children however are proportionate to their noses. Although my daughter's is larger, her eyes are farther apart, etc. I think it's more about the proportion in relation to the child's other features. My sister got the bigger nose, but also has large eyes and a wide full mouth. She's beautiful! And I personally think big noses on men are attractive (obviously, lol).
What is the probability?
First, although the question calls for a Punnet Square, it can easily be discussed without it. If freckles is determined by a dominant allele, F, then both parents are Ff and the probabilities of genotypes of their offspring are in the ratio of 1 FF: 2Ff: 1ff. The son Michael shows the homozygous recessive so each parent contributes an "f". Now, the second question is trickier, and the answer is not what the previous posters state. The question is what is the probability of BOTH of the 2 more children having freckles. Thus one has to multiply the probabilities. The probability of the first having freckles is 3/4, ... the second is 3/4....... so the probability of BOTH is 3/4 x 3/4 or 9/16 or 56%.