How to unlock: Speak with SAM during A Better Beginning main quest [Nexus: Habitation Quarters].
Here you can find the guide for Ryder Family Secrets quest. It is one of the side quests in Mass Effect: Andromeda game. The quest is from "Allies and relationships" category. During this mission you must find memory triggers that are scattered around the world. Those items allow to remove SAM's memory locks and watch Alec Ryder's memories.
Beginning the quest
This quest is automatically added to your journal after the meeting with SAM in Nexus: Habitation Quarters right after the start of the main quest A Better Beginning. Right next to the place where you spoke with the AI you can find Alec Ryder's cabin. Go there and find the first memory trigger. Interact with the object.
Approach the terminal and speak with SAM. The AI unlocks the ability to watch Alec Ryder's first memory. After watching it you can ask SAM additional questions and start searching for other memory triggers.
Memory triggers on planet Eos
The next memory trigger is on the top of a small mountain near the north base on Eos, the one in which you started the exploration - you can see it on the picture. The path to that mountain is west to the item.
The next memory trigger can be found in the place where you establish Eos outpost (this happens during the last part of A Better Beginning quest).
Chapter in progress...
Optional: Visit your sibling in Nexus Cryo Bay
This objective will appear in your journal once you've spoken to Director Tann during the final part of A Better Beginning. Use the rail and travel to Nexus: Cryo Bay. Inside, meet with Doctor Carlyle to ask about the condition of your twin brother/sister. Now you can attempt to communicate with your sibling. This "meeting" will enable you to lie about the past events or tell the truth about the death of your father and the situation on Eos.