Goddess Saraswati is daughter of Brahma. Goddess Saraswati was born from the body of Brahma similar to her 10 brothers.
They were also born from the body parts of Brahma like Marichi Rishi , Atri Rishi , Angirasa Rishi, Pulaha Rishi, Pulutsya Rishi, Krathu Rishi, Vashistha, Prachethasa, Bhrigu and Narada Muni.
Reference in Shrimad Bhagavata Purana:
There is a conversation between Rishi Maitreya & Vidura in Srimad Bhagavata Purana 3.12.28
हृदि कामो भ्रुव: क्रोधो लोभश्चाधरदच्छदात् ।
आस्याद्वाक्सिन्धवो मेढ्रान्निऋर्ति: पायोरघाश्रय: ॥ – Srimad Bhagavata Purana 3.12.26
Desire (काम) became manifested from the heart of Brahmā, anger (क्रोध) from between his eyebrows, greed (लोभ) from between his lips, Speech (वाक्) from his mouth, the ocean (सिन्धु) from his penis, and from his anus, the caretaker of all sins (निऋर्ति).
वाचं दुहितरं तन्वीं स्वयम्भूर्हरतीं मनः । – Srimad Bhagavata Purana 3.12.28
“Oh Vidura, we have heard that the daughter Vâk who was born from his body distracted the mind of Brahmâ”
*An another name for Saraswati is “goddess of speech” ( वाक्, वाङ्मयी, वाग्देवी)