Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 18: The Advent of Rāma, Lakṣmaṇa, Bharata and Śatrughna
Text 1.18.14

अथ लक्ष्मणशत्रुघ्नौ सुमित्राजनयत्सुतौ।
सर्वास्त्रकुशलौ वीरौ विष्णोरर्धसमन्वितौ॥

atha lakṣmaṇa-śatrughnau sumitrājanayat sutau
sarvāstra-kuśalau
vīrau viṣṇor ardha-samanvitau

atha = after Bharata’s birth; lakṣmaṇa-śatrughnau = Lakṣmaṇa and Śatrughna; sumitrā = Sumitrā; ajanayat = gave birth to; sutau = two sons; sarva-astra-kuśalau = they were expert in all weapons; vīrau = and heroic; viṣṇoḥ = from Lord Viṣṇu; ardha-samanvitau = they were manifested from portions of the pāyasa that came.

After Bharata’s birth, Sumitrā gave birth to two sons, Lakṣmaṇa and Śatrughna. They were expert in all weapons and heroic. They were manifested from portions of the pāyasa that came from Lord Viṣṇu.

Lakṣmaṇa and Śatrughna were twins. Ardha here simply means “a portion.”[10] Ardha-samanvitau indicates that Lakṣmaṇa and Śatrughna were manifested from portions of the pāyasa that Lord Viṣṇu had sent.

[10] bhittaṁ śakala-khaṇḍe puṁsy ardho ’rdhaṁ same ’ṁśake. (Amara)