Short answer
Material facts about previous marriages should be disclosed honestly before marriage.
Islamic Guidance
What Islam teaches
Truthfulness and avoidance of deception are fundamental Islamic principles. A person's marital history can materially affect another person's decision.
Practical Guidance
What you can consider
Provide accurate marital-status information and discuss relevant circumstances respectfully. Do not hide a previous marriage in order to secure acceptance.
Sources
Qur'an 33:70; Qur'an 2:228.