How do we know brotherly love is true?

True brotherly love, as highlighted in Romans 12:9-10, must be without dissimulation, meaning it should be genuine and without pretense. This sincere affection is possible because it is rooted in the love Christ first showed us. As Scripture states, 'We love Him because He first loved us' (1 John 4:19). In reflecting on this unconditional love, believers are called to express genuine care and affection for one another, fostering unity and a spirit of cooperation that embodies the essence of brotherhood in Christ. Ultimately, our love must stem from our shared identity as children of God, through which we are empowered to love sincerely.