The phrase "steadfast relationship" is correct and usable in written English.
It is typically used to describe a strong and unwavering bond or connection between two individuals or entities. Example: Despite the challenges and obstacles they faced, John and Mary's steadfast relationship remained unshakeable, standing the test of time.
As Ambassador Stevens well understood, American foreign aid, in the form of economic assistance to provide humanitarian relief, is perhaps our greatest asset to forge steadfast relationships with billions of people in nations in every corner of the globe.
For some of us, it's a more steadfast, stable relationship than the one we have with our Valentine.
And his past relations, I believe ― and I'm very cautious about this ― but I believe that Mr. Tillerson understands the importance of a steadfast and strong relationship".
HBO says it did not ask Kenney Baden to break privilege, and from the inception of "our relationship she was steadfast in insisting that she maintain that privilege".
Hillary Clinton, the Democratic contender to replace Obama in this year's presidential elections, said Washington should "make clear America's steadfast commitment to the special relationship with Britain and the transatlantic alliance with Europe".
Elsewhere, Nehring interrogates our steadfast insistence on balanced, healthy relationships, our readiness to condemn doomed, impossible entanglements.
Prime Minister Malcolm Turnbull visited New Zealand last month, where leaders of both countries reiterated their "special relationship," although Turnbull remained steadfast on his policy of deportation.
I have to say that she was not steadfast because she approved of my gay relationship.
Clearly her steadfast devotion to Monk's music propelled their relationship, which both maintained was platonic.
