From an Integral perspective all humans are simultaneously whole and part. Like a whole hand that is part of a whole body. Or a whole finger that is part of a whole hand. Or a whole letter that is part of a whole word. Each part has to maintain its wholeness to be a part of the larger whole. The whole is always larger and has more value (or depth) than the sum of its parts. Just imagine how many things a hand can’t do without the other. This is true for relationships as well. To answer the first question; yes, we need a partner to co-create a new whole, which we call a couple. The answer to the second question is no, but we need to be compatible or complementary in order to create synergy (like two hands). Simply put, two letters like I (II) don’t form a word. But two different letters do, like “we” or “us”.
On a physical level, we are usually male or female, with sperms and eggs. On an energetic level, we are either feminine (following, receiving, full, dark, descending, communal, etc.) or masculine (leading, giving, empty, light, ascending, agentic, etc.). On a mental level, nobody knows everything, so two minds are better than one. On an emotional level, we all have different relational childhood and attachment wounds that we can only heal in a love relationship. On a spiritual level, only couples can challenge each other to love unconditionally and awaken at the level of all seven chakras through tantric practices.