"closer relationships" is correct and usable in written English.
For example, "Developing closer relationships with our customers has led to higher loyalty over time."
His commitment to closer relationships between religions was strong.
A.D.M. also wants to build closer relationships with farmers.
Some have forged closer relationships with their children.
There's daily contact, and there may be more clashes but closer relationships too.
When we connect and share, we build closer relationships with the people we love".
To that end, several of the company's initiatives are aimed at building closer relationships with suppliers.
"It's about building closer relationships with students, and universities have got a lot better at it".
I'd particularly like to see closer relationships between schools and local manufacturing hubs.
Managers at SABMiller, too, have formed closer relationships with suppliers and sellers.
Havas plans to respond by forging closer relationships with its clients.
However, someone familiar with Blair's business activities suggested he is keen to cultivate closer relationships with Russian oligarchs.
