You can gift up to $14.5K (from my memory) per gifter and per giftee. To illustrate, I and my wife can give 2 * (14.5K) to each of the giftees. For a family of 4, there are 4 giftees.
The above $14.5K is the
market price of the security. The cost basis is from the gifter if it is
a gain and it is not if it is a loss. Consult your lawyer.
In most cases, it is advantageous to give appreciated stocks to a family member whose tax bracket is lower.