Quick answer
Competence can outrank birth. The verse describes a household where the outsider ends up managing the heir.
Read both lines
The claim would have been startling in a world organized around inheritance. Position in this verse is not fixed by blood, and the servant does not merely get promoted; he ends up sharing what was supposed to belong to sons only. Proverbs is not proposing a social program here. It is observing that capability tends to find its level over time, in households as elsewhere, and that a family cannot indefinitely protect a son who will not learn. The book will say the same thing about a king's servant at 14:35.
Related: Proverbs 14:35 · Proverbs 12:24 · Proverbs 10:5
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.