2. In a certain kingdom, there are 32 knights, some of whom are servants to other knights. Each servant can have at most one master, and each master must be richer than any of his servants. If a knight has at least four servants, he is ennobled as a noble. If it is stipulated that a servant of $A$'s servant is not a servant of $A$, then the maximum possible number of nobles is $\qquad$
2.7.

According to the problem, the richest knight is not a servant of any other knight, so at most 31 knights can be servants of other knights.

Since each noble has at least four servants, there can be at most 7 nobles.

Number the 32 knights as $1,2, \cdots, 32$, with wealth decreasing as the number increases, then
$$
\begin{array}{l}
1(2,3,4,5) ; \quad 5(6,7,8,9) ; \\
9(10,11,12,13) ; 13(14,15,16,17) ; \\
17(18,19,20,21) ; 21(22,23,24,25) ; \\
25(26,27,28,29),
\end{array}
$$

Each knight outside the parentheses is a noble, and the knights inside the parentheses are servants.
This shows that 7 nobles are possible.