Short answer. You can share your own stake with an associate, but you cannot make him a partner alone. Under Article 1804, every partner may associate another person with him in his share, yet that associate cannot be admitted into the partnership without the consent of all the other partners — even if the partner who brought him in is a manager.
What the law says
the associate shall not be admitted into the partnership without the consent of all the other partners
Civil Code, Article 1804 — Sub-Partner (Associate). Read the full provision →
You may bring in an associate — for your share only
Article 1804 recognises a limited freedom and a firm limit in the same breath. The freedom: every partner may associate another person with him in his share. You can take someone in on your own stake and share with him the profits and losses that fall to you. This creates what is often called a sub-partnership: an arrangement between you and your associate, sitting behind your position in the firm. It is your private affair, made with your own share, and for that you do not need anyone else's permission. The associate's rights run against you, not against the partnership.
The associate is not a partner
The limit is equally clear: the associate shall not be admitted into the partnership without the consent of all the other partners. Bringing someone into your share does not make him a member of the firm. He has no standing as a partner — no say in management, no direct claim against the partnership, no automatic access to its books — unless every existing partner agrees to admit him. And the consent required is unanimous: all the other partners, not a majority. The reason is the personal nature of a partnership.
Even a managing partner cannot do it
The article closes off the obvious loophole. It applies even if the partner having an associate should be a manager. A partner who runs the firm might assume his management authority lets him bring his associate in as a full partner. It does not. However much power a managing partner has over the firm's ordinary affairs, admitting a new partner is not an act of ordinary management; it changes the membership of the partnership itself, and that requires the unanimous consent of the others regardless of who is asking.
What this means in practice
For a founder, the practical points are two. If you want to bring in outside money or a helper without disturbing the firm, you can do it through your own share as a sub-partnership — but understand that your associate is your counterpart, not the firm's, and the other partners owe him nothing. If instead you want that person to become an actual partner — with a voice in the business and a direct stake — you need the agreement of every other partner, and no title or management role of yours can substitute for it. Put any such admission to the whole partnership, and get the consent in writing.